Here is a Photoshop image of the patterns I have used. The blue area can be trimmed out for split finger tabs.
For the most part self explanatory but the tabs I make for myself are traced from my three fingers on the back
of the leather.
Once I trim the width and finger hole/holes for fit I will put the tab on and grab the string as I would when shooting.
While holding the string I will make additional traces along my finger tips and then trim off the excess leather and even
out the outline.
Removing the excess leather makes it look too small at first glance but once you engage the string you will see that you only
the leather required to do the job and not get in the way.
True Cordovan leather is the best I have found for tabs. With use it softens but doesn't loose it's slickness and if you don't
lose it will last for years.
Good Luck